Some parts inside the body are soft: the brain, the heart and the lungs.

Round the brain sits a hard case of bone. That case of bone is the skull.

A knock on the head hits the skull, not the brain.

Round the heart and lungs sits a cage of long, curved bones. Those bones are the ribs.

The soft parts inside: the pink brain inside the skull, and the red heart between the two pink lungs inside the ribs.

The skull protects the brain, and the ribs protect the heart and lungs.

Two bones and the soft part each one protects.